Rojo joins Ander Herrera, Luke Shaw and Vanja Milinkovic to take the transfer outlay soaring past £70m in the process.

The Old Trafford side also confirmed that Portuguese winger Nani will be heading to Sporting on loan for the season as part of the deal.

The Argentine said: "It is such an honour to say that I now play for Manchester United. The Premier League is the most exciting league in the world and to have the chance to play in it for the world's biggest club is a dream for me."

"I am young and am very keen to continue to learn the game, so playing for such an experienced technical coach as Louis van Gaal is a fantastic opportunity for me. I have joined United to work hard with my team-mates to win trophies and I know that the manager shares that ambition."

Louis van Gaal was quick to praise his new acquisition: "Marcos is a very gifted defender," he told the Manchester United webstie.

"He has played at the highest level in world football and can play either as a central defender or left-back. He has ability, physical strength and a willingness to learn that means he has a very bright future ahead of him. He had a very strong World Cup and has been playing in Europe for a couple of years now. He is a very good addition to the team."